A variety of radiative or far-field, and non-radiative or near-field, energy or power transfer techniques are known. For example, radiative wireless information transfer using low-directionality antennas, such as those used in radio and cellular communications systems and home computer networks, may be considered wireless energy transfer. As will be appreciated, this type of radiative energy transfer is inefficient because only a small portion of the supplied or radiated power, namely, that portion in the direction of, and overlapping with, the receiver is picked up. The vast majority of the power is radiated in other directions and lost in free space. Such inefficient energy transfer may be acceptable for data transmission, but is not practical when trying to transfer useful amounts of electrical energy for the purpose of doing work, such as for example, powering or charging electrical or electronic devices. One way to improve the transfer efficiency of some radiative energy transfer schemes is to use directional antennas to confine and preferentially direct a beam of radiated energy towards a receiver. However, these directed radiation schemes typically require an uninterruptible line-of-sight between the transmitter and receiver as well as potentially complicated tracking and steering mechanisms in the case of mobile transmitters and/or receivers. In addition, such directed radiation schemes may pose hazards to objects or people that cross or intersect the beam of radiated energy when modest to high power beams of energy are being transmitted.
A known non-radiative, or near-field, wireless power transmission system, often referred to as either induction or traditional induction, does not (intentionally) radiate power, but instead uses an alternating current passing through a primary coil, to generate an alternating magnetic near-field that induces currents in a near-by receiving or secondary coil. Induction schemes of this nature have demonstrated the ability to transmit modest to large amounts of power, however only over very short distances, and with very small offset tolerances between the primary coil and the secondary coil. Electric transformers and proximity chargers are examples of devices that utilize this known short range, near-field energy transfer scheme.
PCT Application Publication No. WO 2009/089146 discloses a wireless power transmission system that includes a transmitter and a receiver. The transmitter includes a radio frequency energy generator, a first transmitting plate, and a second transmitting plate. The first transmitting plate is operatively coupled to the radio frequency energy generator. The second transmitting plate is operatively coupled to ground. The receiver includes a rectifier, a first receiving plate, and a second receiving plate. The first receiving plate is operatively coupled to the rectifier. The first receiving plate is configured to be capacitively coupled to the first transmitting plate and the second receiving plate is configured to be capacitively coupled to the second transmitting plate. The second receiving plate is operatively coupled to ground.
U.S. Patent Application Publication No. 20110198939 discloses a transmitter that includes a substantially two-dimensional high-Q resonator structure including a flat coil and an impedance-matching structure operably connected to the resonator structure. The transmitter is configured to transmit power wirelessly to another high-Q resonator.
U.S. Patent Application Publication No. 20090206675 discloses means for transporting electrical energy and/or information from a distance by using, at a slowly varying regime, the Coulomb field which surrounds any set of charged conductors. A device is composed of energy production and consumption devices situated a short distance apart, and it uses neither the propagation of electromagnetic waves nor induction and cannot be reduced to a simple arrangement of electrical capacitors. The device is modeled in the form of an interaction between oscillating asymmetric electric dipoles, consisting of a high-frequency high-voltage generator or of a high-frequency high-voltage load placed between two electrodes. The dipoles exert a mutual influence on one another. The device is suitable for powering industrial and domestic electrical apparatus and is especially suitable for powering low-power devices moving in an environment and for short-distance non-radiating transmission of information.
Although wireless power transmission techniques are known, improvements are desired. It is therefore an object to provide a novel wireless electric field power transmission system, a transmitter and receiver therefor and a method of wirelessly transmitting power.